The present invention relates to a semiconductor device having a heat-sink attached thereto, and more particularly, to an attachment configuration of a heat-sink to a package of a semiconductor device.
In most instances, heat-sinks, that is, heat radiators are attached to packages of semiconductor devices to efficiently disperse heat generated in semiconductor chips installed in the packages thereby cooling the chips. Typically, the heat-sink is favourably installed in a so-called face-down semiconductor device because of its easy attachment. The face-down type device, however, restricts the number of the outer leads which are led out from the package because the leading-out portion of the package is limited to a periphery of its planar surface. On the other hand, a recent progress on functions of a semiconductor chip has brought about increase in necessary number of outer leads. To meet this demand, a so-called face-up type semiconductor device is more convenient because the outer leads can be led out from the all parts of one plane surface of the package. In the face-up type device, a heat-sink is attached to peripheral parts of the other planar surface of the package, and to transfer the heat from the package to the heat-sink with a conductance as high as possible, the heat-sink would be attached all around as if a closed cavity is formed between the center of the package and that of the heat-sink. In a view of the reduction in manufacturing cost of the device, usage of resin as adhesive between the heat-sink and the package is beneficial.
The process for fabricating the above-mentioned heat-sink attached semiconductor device comprises the step of attaching a heat-sink to a package with a resin placed between them, which needs a cure step of the resin at a high temperature to provide good adhesion.
This cure is carried out in such a condition that the resin is placed between the planar attachment surface of the heat-sink and the package to allow a cavity defined by the heat-sink and the package. Thus during the cure period, the pressure inside the cavity may be increased to a degree to force the molten resin outwards with a result in making the adhesion for the attachment thinner and smaller in strength at parts thereof which are randomly positioned or in bringing about a burst at parts randomly positioned. Such the uneven adhesion decreases the adhesive strength and lowers the heat dissipation effect thereby impairing the product reliability.